I worked in a doctor's office for a few years as a medical assistant. Most appointment slots were double or triple booked, though I would double book an office visit with something that took a minute or two like a wound redressing or if a patient was a known, serial no-show. Part of my job was keeping the rooms moving. I don't think anyone ever waited more than 20 minutes unless there was a patient that took an inordinately long time with their appointment because of a complex issue.
We used to have this one elderly woman who always wanted the first appointment in the morning at 8am. She would then proceed to show up at 7:30, before any of us had even arrived to open the office, and then complain that she had to wait in her car. She would do this every time she had an appointment. Had she shown up at her actual appointment time, her wait would've been less than 5 minutes.
Keeping you waiting over an hour past your appointment time is ridiculous. There is only one doctor I'll wait that long for, and it's my neurologist because she actually listens to me, which is a rarity. I actually have an appointment with her Monday at 11am. Between waiting and the actual procedure, I'm sure I'll not be out of there before 1pm. Every other neurologist I've seen has been a raging, arrogant asshole, to the point where I thought it might've been a prerequisite for choosing that specialty.